Establishes delegate parser t as a single token of tab completion.
When tab completion of part of this token is requested, description is displayed for suggestions and no completions are ever performed.

Establishes delegate parser t as a single token of tab completion.
When tab completion of part of this token is requested, no completions are returned if hide returns true for the current tab completion level.
Otherwise, the completions provided by the delegate t or a later derivative are appended to the prefix String already seen by this parser.

Establishes delegate parser t as a single token of tab completion.
When tab completion of part of this token is requested, the completions provided by the delegate t or a later derivative are appended to
the prefix String already seen by this parser.

Establishes delegate parser t as a single token of tab completion.
When tab completion of part of this token is requested, display is used as the printed suggestion, but the completions from the delegate
parser t are used to complete if unambiguous.